1. Field of the Invention
In general, the present invention relates to a coding apparatus, a coding method adopted by the coding apparatus and a coding program implementing the coding method. In particular, the present invention relates to a coding apparatus capable of reducing a bit error rate, a coding method adopted by the coding apparatus and a coding program implementing the coding method.
2. Description of the Related Art
In recent years, in an operation to encode digital data by making use of error correction codes or encode digital data in accordance with RLL (Run Length Limited) codes and store the result of the coding operation in an apparatus such as a magnetic-tape recording apparatus or an optical-disc apparatus, an interleaving technology for coding the digital data by combining the error correction codes with an interleaving technique is adopted in order to allow errors to be corrected with a high degree of efficiency. Also before digital data is transmitted in a multi-input multi-output transmission system, the digital data is encoded by adoption of the interleaving technology for coding the digital data by combining error correction codes with the interleaving technique.
The RLL code is a code for encoding input data so that the maximum number of consecutive 0 bits or 1 bits to be stored in a recording apparatus or transmitted in a transmission system is limited to a finite number. The RLL code is used widely in fields such as a high-density magnetic recording field and a high-speed transmission field. For example, an 8b10b code limits the maximum number of consecutive 0 bits or 1 bits to an integer not greater than 5. The 8b10b code is widely used in high-speed transmission systems such as a PCI (Peripheral Component Interconnect) Express transmission system and a gigabit Ethernet transmission system. In addition, a TMDS (Transition Minimized Differential Signaling) used in a digital-video transmission system at an HDMI (High Definition Multimedia Interface) is used for such a purpose.
On the other hand, the error correction code is a code for encoding input data so that errors contained in the encoded data can be corrected. Errors contained in the encoded data are errors generated in operations to store the data into a recording medium, reproduce the data from a recording medium and transmit the data in a transmission system.
Technologies relevant to the RLL code and the error correction code are described in documents such as U.S. Pat. No. 5,717,395 entitled “Rate 16/17 ENDEC with independent high/low byte decoding” and U.S. Pat. No. 6,567,951 entitled “Optical disc format exhibiting robust error correction coding,” hereinafter each referred to as Patent Documents 1 and 2, as well as “8 mm Wide Magnetic Tape Cartridge for Information Interchange Helical Scan Recording=AIT-3 Format,” Standard ECMA-329, December 2001. and “12.7 mm-384-Track Magnetic Tape Cartridges—Ultrium-1 Format,” Standard ECMA-319, June 2001, hereinafter each referred to as Non-Patent Documents 1 and 2.